Numerous examples of prototype and commercially available line sensors derive power form a primary cell storage battery that both limits and defines operational and communications availability (examples include SEL fault current indicators). A limited number of line sensors may include rechargeable cells harvesting solar energy and/or the electromagnetic field of the conductor to extend operational and communications availability (GridSentry and others).
Harvesting energy from the electromagnetic field in the proximity of the conductor can be engineered with magnetic cores around the conductor, capturing the magnetic field created by line current flow and transforming it to an AC voltage. Split-core toroidal transformers can be mounted around a conductor, eliminating the need to cut and splice the conductors. The design of split-core transformers for general use as power current measurement devices is routine for applications in mild environmental conditions. However, successful implementation of environmentally robust split-core transformers satisfying the full range of product requirements provides additional challenges due to extreme weather and environmental elements that can degrade the performance and lifetime of split-core transformers.